JetBlue (NASDAQ:JBLU) CEO David Barger likely will have a few things to crow about when his company reports fourth-quarter and full-year 2011 earnings on Jan. 26: year-over-year revenue growth, capacity growth — particularly in Boston and the Caribbean — and stronger off-peak revenue performance.

The carrier also has a bit to boast about in its ancillary-revenue growth. Because of initiatives such as JetBlue’s roomier “Even More Space” seats, aimed at premium business travelers, revenue per passenger had risen by $19 in the third quarter of last year. That 7% year-over-year likely continued through the fourth quarter.

In many ways, JetBlue’s business model is a hybrid of low-cost carrier and legacy airline — a tough tightrope to walk in the infamously low-margin airline business. While it retains its identity as a low-cost carrier, JetBlue’s hubs and interline agreements (which allow passengers to book flight segments and transfer baggage among multiple airlines) appear more legacy and less budget. JBLU caters to the leisure market, most notably Florida and Latin America, while still staking a claim on premium business travelers at Boston’s Logan and New York’s JFK.

JetBlue’s success to date lies in its ability to sell low cost and differentiation; ancillary fees and unique perks, such as its LiveTV offering that will begin testing in-flight broadband wireless connectivity to customer devices such as Apple (NASDAQ:AAPL) iPads later this year. It also has been able to keep costs low via its nonunion workforce and young aircraft fleet.

Although the company’s customer-service ratings are high, JBLU got a huge black eye last October when a freak storm stranded passengers on a tarmac for seven hours. Still, the balance sheet is strong, and the stock is up more than 60% since then. However, JetBlue shares could see turbulence given the headwinds the carrier faces in 2012:

1. Fuel Prices. Expect JBLU executives to lament the impact of fuel-price volatility on fourth-quarter and full-year earnings next Thursday. The airline’s fuel expense was up by more than 40% in the third quarter and likely did not improve in the fourth. Even worse, the airline’s fuel-hedging program was, as Barger said in a recent TV interview, “catastrophic.” Since fuel accounts for about 40% of airline costs, and all signs point to continued price volatility this year, JBLU will have to work harder to minimize the impact of bad surprises.

2. Operating Costs. JBLU has been able to cut costs by lowering employee wages and benefits by about 4% year-over-year. But those costs will rise over time as crew seniority increases, putting greater pressure on the carrier’s margins. Although JetBlue’s fleet is very young compared with those of most airlines, the planes are getting older and more expensive to maintain. JBLU’s maintenance costs likely were about 25% higher last year than they were in 2010.

3. Competition. JetBlue faces tougher competition with Delta (NYSE:DAL) in the wake of its “slot-swap” with US Airways (NYSE:LCC). Delta will now compete head to head with JetBlue on domestic routes out of Kennedy — a big reason Dahlman Rose downgraded JBLU from “hold” to “sell” on Tuesday. And don’t forget, if American Airlines (PINK:AAMRQ) is acquired by a rival, such as Delta or US Airways, any economies of scale gained could put further pressure on JBLU.

JBLU is trading at about $5.50 now. With a market cap of $1.6 billion, it has a price-to-earnings-growth ratio of nearly 3.7, indicating that the stock is overvalued. JBLU’s one-year performance is –16%. I have a short-term hold on it — there is value in the company’s business model, but the 2012 outlook is too hazy at this point.

As of this writing, the author did not hold a position in any of the stocks named here.